Battery Questions

Hello,

The battery that came with my 2017 5th wheel took a complete charge and I unhooked it from charger planning on putting it back in the 5th wheel but I got delayed by a few days. Today I went to put it back and decided to check the charge level (using my battery charger) and discovered that it dropped by almost 50% in about 6 days. The battery is a Deka Marine Master 625 CCA battery. It is not an AGM battery. I have always kept the water/acid topped off using only distilled water. It is just over two years old based on date I got the RV.

In my previous 5th wheel I had an Optima Blue Top battery. I was very happy with that battery as it performed well and no maintenance other than putting a full charge in it every spring.

If I have to replace the Deka battery I was looking at the Optima batteries and saw two that would fit my battery box.

Optima Blue Top Marine Battery, Group Size D34M, 750 CCA $276.00
Specifications
Cold Cranking Amperage:
750 A
Cranking Amperage:
870 A
Negative Terminal Location:
Top Right
Positive Terminal Location:
Top Left
Reserve Capacity:
120 min
Terminal Type:
Top Mount
Voltage:
12.0 VDC

Optima Blue Top Marine Battery, Group Size 27M, 800 CCA $298.00
Specifications
Cold Cranking Amperage:
800 A
Cranking Amperage:
1000 A
Negative Terminal Location:
Top Left
Positive Terminal Location:
Top Right
Reserve Capacity:
140 min
Terminal Type:
Top Mount
Voltage:
12.0 VDC

Now since the battery is only used to supply 12 volt power to my 5th wheel the cranking capacity really doesn't mean anything to me right?

I should really be concerned with the reserve capacity if my thought process is correct. So the real difference is 20 minutes additional reserve capacity for an additional cost of $22.00.

We do not as of now boondock other than an overnight in a rest area on occasion. I do have a small inverter hooked up to be able to make coffee etc. when needed.

Is the extra 20 minutes worth the $22.00?

Are there better maintenance free batteries that I should consider?

Thanks in advance for your input!

Dave

Airdaile
Explorer
Jun 10, 2019
The only number you need to look at is the reserve capacity. That's how many minutes it takes to discharge a fully charged battery at 20 amps per hour. Whether it's worth another $22, it depends on how you plan to use you camper. If you're plugged in most of the time, either battery will do. If you plan to do extensive boondocking, neither battery will do.
2oldman
Explorer II
Jun 10, 2019
For just a bit more money get a Lifeline AGM. This one, GPL-27T. Optimas are just not a good choice for RVs.
KD4UPL
Explorer
Jun 10, 2019
You say you checked the charge level using your charger? How does that work? Have you checked the battery's resting voltage? If it's 12.6 or 12.7 it should be fine.
In my opinion Optima batteries are overpriced for what they are. I've installed hundreds of Deka batteries over the years along with lots of Rolls and Lifeline. I've had very good results form all of them.
You have just one battery but use it to power an inverter running a coffee maker? That is very hard on that battery. If you have a 1,200 watt coffee maker I would think you would want at least 600 AH of battery hooked to the inverter.
dpgllg
Explorer
Jun 10, 2019
2oldman wrote:
For just a bit more money get a Lifeline AGM. This one, GPL-27T. Optimas are just not a good choice for RVs.

I'm curious why the Optima's are not a good choice for RV's?
dpgllg
Explorer
Jun 10, 2019
KD4UPL wrote:
You say you checked the charge level using your charger? How does that work? Have you checked the battery's resting voltage? If it's 12.6 or 12.7 it should be fine.
In my opinion Optima batteries are overpriced for what they are. I've installed hundreds of Deka batteries over the years along with lots of Rolls and Lifeline. I've had very good results form all of them.
You have just one battery but use it to power an inverter running a coffee maker? That is very hard on that battery. If you have a 1,200 watt coffee maker I would think you would want at least 600 AH of battery hooked to the inverter.

My battery charger has a gauge that indicates the battery strength when connected. It has a 12 volt deep cycle setting to charge the RV battery. When fully charged it indicates the amount of charge ( I can't remember exactly what the numbers are). It is probably not real accurate but enough to let you know that when you hook up the battery the amount of charge in it.

When I say making coffee we make two cups on a Kurig and that's it. We have only done this twice with this battery. I can turn the inverter off so it is not running all of the time just when I need it.

You say that you have installed hundreds of batteries over the years. Are you in the business? If so what battery and size would you go with and why?
wa8yxm
Explorer III
Jun 10, 2019
The number you need is AMP HOURS.. for OPTIMA a Group 27 is about 60 amp hours give or take a couple.. A non-optima AGM (Cheaper) is `100 amp hours. and a flooded wet battery (Cheapest) is also 100 amp hours.

I should add weight is heavier in the non optima types as well about the same 6/10 ratio since weight and amp hours are directly related.

Finally MARINE/deep cycle like the Marine Master.. NOT THE BEST choice
DEEP CYCLE.. Like a GC-12.. (If it will fit) much better for house use.

Deka stores may have a DEEP CYCLE in the 27/31 format as well.. I DO NOT KNOW. My Deka's are G-20s (A GC-2 class) 6 volt in series.
2oldman
Explorer II
Jun 10, 2019
dpgllg wrote:
I'm curious why the Optima's are not a good choice for RV's?
They are pretty, but they're not deep cycle batteries. Lifelines are much better quality, in my opinion.
theoldwizard1
Explorer II
Jun 11, 2019
dpgllg wrote:
Now since the battery is only used to supply 12 volt power to my 5th wheel the cranking capacity really doesn't mean anything to me right?

I should really be concerned with the reserve capacity if my thought process is correct.

If you don't boondock and only occasionally use the inverter, just buy the largest, CHEAPEST, regular, automotive starting battery that will fit in your battery box. You will pay a LOT of money for the convenience of an AGM.

Worst case, you may have to start the tow vehicle engine and hook the inverter up directly to its battery to run the inverter for that morning "cup of Joe".

Just make sure your converter is properly charging your battery when you get plugged in.
KD4UPL
Explorer
Jun 11, 2019
dpgllg wrote:
KD4UPL wrote:
You say you checked the charge level using your charger? How does that work? Have you checked the battery's resting voltage? If it's 12.6 or 12.7 it should be fine.
In my opinion Optima batteries are overpriced for what they are. I've installed hundreds of Deka batteries over the years along with lots of Rolls and Lifeline. I've had very good results form all of them.
You have just one battery but use it to power an inverter running a coffee maker? That is very hard on that battery. If you have a 1,200 watt coffee maker I would think you would want at least 600 AH of battery hooked to the inverter.

My battery charger has a gauge that indicates the battery strength when connected. It has a 12 volt deep cycle setting to charge the RV battery. When fully charged it indicates the amount of charge ( I can't remember exactly what the numbers are). It is probably not real accurate but enough to let you know that when you hook up the battery the amount of charge in it.

When I say making coffee we make two cups on a Kurig and that's it. We have only done this twice with this battery. I can turn the inverter off so it is not running all of the time just when I need it.

You say that you have installed hundreds of batteries over the years. Are you in the business? If so what battery and size would you go with and why?

My wife's Kuirg uses 1,425 watts AC. Pulling that thru an inverter will likely be about 140 amps. That is an enormous draw on a 100 AH battery. It's best to not draw above about a C/5 rate; that is the Capacity in AH divided by 5. So, for a 140 A draw you would want 700 Ah. It's not that you can't do it with less, it's just harder on the battery, the voltage sags more, etc.
I'm an electrical contractor who specializes in solar systems, particularly off-grid homes and cabins. I would install 2 6v golf cart batteries in series rather than 1 or more 12v batteries. That will give you about 220 AH. If you want more I'd use 2 sets of 6v GC batteries for 440 AH.
MEXICOWANDERER
Explorer
Jun 11, 2019
A group 34 battery is a 24 that has been topped to make it shorter. To clear the hood. Auto manufacturers are so sloppy they did not care that the top of my toad's battery posts are 10" from the hood and the tray is 15" long. They just don't give a ****. The 24 is 17% more battery that costs them LESS than a group 34. it's a mopar. Can't cure stupid.

'

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